Due to the intense stress of studying, the tired female student Kimura decided to masturbate to relax and relieve some of her own stress. Unfortunately, nothing is perfect, while masturbating, her older brother who had just returned home from drinking with friends caught her in the act. Discovering his younger sister masturbating while still intoxicated, he forced her to have sex with him. Partly out of fear of what he might do, and partly out of fear of their parents finding out because he threatened to tell them, she had no choice but to helplessly submit to whatever her despicable older brother wanted to do.